Messaging: New feature 'Add X-MDN to POST Http header for carrier

Set x-MDN as empty in default sub_mms_config file

Change-Id: Icfe268eeb5829c8c6e6f8fa0f17d2d1cf07fc950
diff --git a/res/xml/sub_mms_config.xml b/res/xml/sub_mms_config.xml
index 11c89c8..9bb2503 100755
--- a/res/xml/sub_mms_config.xml
+++ b/res/xml/sub_mms_config.xml
@@ -27,4 +27,5 @@
 IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -->
 
 <mms_config version="4">
+    <string name="httpParams"></string>
 </mms_config>